lonmin=-5.5
lonmax=8.5
latmin=42
latmax=51.5
paslon=1/30
paslat=1/40

data=load("raf09.mnt");
data=reshape(data,2,length(data)/2);
data=data(1,:)';
sizelon=(lonmax-lonmin)/paslon+1;
sizelat=(latmax-latmin)/paslat+1;

data=reshape(data,sizelon,sizelat)';

lat=48.84105487;
lon=2.58730777;

indlat=floor((latmax-lat)/paslat)+1;
indlon=floor((lon-lonmin)/paslon)+1;

dlon=lon-paslon*(indlon-1)-lonmin;
dlat=latmax-paslat*(indlat-1)-lat;

data=data((indlat):(indlat+1),(indlon):(indlon+1))



val1=(data(3)-data(1))/paslon*dlon+data(1);
val2=(data(4)-data(2))/paslon*dlon+data(2);
val=(val2-val1)/paslat*dlat+val1
